Biomedical subjects

J Dauper

Publications and source records attributed to J Dauper.

3 recordsLinked to original sources

PubMed1990

[Clinical value of new tonometers].

In a clinical study four different tonometers [a hand-held applanation tonometer (HAT), a tonometer that works according to the principle of Mackay-Marg and two noncontact tonometers (NCT A und NCT B)] were compared with respect to accuracy and precision. In a randomized sequence, two physicians took six measurements of both eyes of 99 patients using the four different instruments. The interval between the two measurements in one eye was 3 min. The correlations of repetitive measurements for one tonometer in one eye showed good results for HAT (r = 0.985, SD = 1.66 mmHg), but significantly worse values for the other three tonometers (Mackay-Marg type: r = 0.85, SD = 3.5 mmHg; NCT A and NCT B: r = 0.91, SD = 2.93 mmHg). To establish the accuracy, the pressure values of the Mackay-Marg type and NCT A and NCT B were compared with those of the well-established HAT. The results were as follows: Mackay-Marg type: r = 0.84, SD = 3.78 mmHg; NCT A: r = 0.86, SD = 4.55 mmHg; NCT B: r = 0.89, SD = 3.26 mmHg). We conclude that the three tonometers tested (one based on the Mackay-Marg principle and the other two on the non-contact principle) are not suitable for clinical and scientific use.

Adolescent↗

PubMed1989

Microprocessor controlled tonometry.

Microprocessors have enabled new techniques to be applied to the design of tonometers. Three new microprocessor controlled tonometers, one operating to the principle of Mackay-Marg (Tono-Pen) and two non-contact airstream tonometers (Pulsair and CT-10) have been examined using as a reference Goldmann and the Hand Held Applanation Tonometers (Draeger-HAT) which used the Goldmann applanation principle. The non-contact tonometers produce a conically formed airstream with top speeds of 90 m/s (CT-10) and 70 m/s (Pulsair) which at the moment of pressure measurement applanates the cornea exactly with a diameter of 4 mm. The readings of the microprocessor controlled tonometers correlate well with the readings of HAT (Tono-Pen r = 0.8414 and s = 3.783, CT-10 r = 0.8606 and s = 4.5477, Pulsair r = 0.8968 and s = 3.2641, where r is the correlation coefficient and s is the standard deviation in mmHg). Repeated measurements with one tonometer give the following standard deviations (HAT 1.6617, Tono-Pen 3.4969, CT-10 2.9179, Pulsair 2.9434). Although the three new instruments are able to measure the intraocular pressure in a wide range they do not work with the same precision as the classical applanation tonometer.

Evaluation Studies as Topic↗

PubMed1989

[Comparative studies of the calibration of new electronic automatic tonometers].

Over the last years the number of newly developed automatic microprocessor controlled tonometers has been increasing. These devices follow totally different measurement principles. Therefore the physical methods for calibration of these tonometers differ widely. Described is the possibility of calibration of new microprocessor-controlled tonometers. First the Tonopen, which follows the Mackay-Marg principle was tested. Its accuracy in measuring the intraocular pressure and its independency of position was examined. Moreover, the non-contact tonometers were tested. Especially the airstream of non-contact tonometers (CT 10, Pulsair) was measured with a Constant Temperature Anemometer (CTA). The topspeed of the airstream was 335 km/h for the CT 10 and 249 km/h for the Pulsair tonometer. The profile of the airstream was paraboloid. The base measured about 5 mm in diameter. For detection of the effect of the airstream to the cornea, a camera was connected over a special interface with the CT 10 and triggered with a flashlight generator. The airstream produced at the moment of pressure measurement an exact applanation of the cornea with a diameter of about 4 mm. The results demonstrate the possibility of physical calibration, but this does not substitute biometrical measurements.

Calibration↗